614 FXUS64 KBRO 210830 AFDBRO Area Forecast Discussion National Weather Service Brownsville TX 330 AM CDT Sat Aug 21 2021 .SHORT TERM (Now through Sunday): High pressure at the surface and aloft will continue to provide subsidence across the region through the forecast period. Hot and humid conditions will continue today and Sunday with high temperatures near normal. Heat indices each afternoon will reach 105 to 110 degrees across most areas and could briefly exceed 111 degrees across portions of Starr and Zapata counties. Lows tonight will range from the mid 70s across the northern ranchlands to the upper 70s to around 80 near the coast. Major Hurricane Grace made landfall very early this morning along the eastern coast of Mexico, near Tecolutla. Despite strong mid level ridging, a surge of deep tropical moisture has pushed into the Rio Grande Valley. BRO sounding data from last night indicates a precipitable water value of 2.22 inches. Lingering tropical moisture with PWATS of around 2 inches will support isolated to scattered showers and thunderstorms across deep south Texas today. Brownsville radar currently shows some ongoing convection across the coastal waters. The latest 06Z/HRRR suggests some tropical downpours may impact the eastern portions of CWA through mid morning and again later this afternoon. Rain chances will diminish this evening with rain-free conditions expected tonight and Sunday. The main weather impacts from Grace will remain along the coast and offshore as large swells continue to arrive. This may lead to some nuisance flooding, with Gulf water reaching or pushing into the dunes on South Padre Island, especially around high tide which is at 6:26 AM. Therefore, the Coastal Flood Advisory remains in effect until 1 PM this afternoon. The long period swells will also support a High Risk of rip currents today through Sunday. Have extend the High Rip Current Statement through 7 AM Sunday. .LONG TERM (Sunday Night through Friday): A robust 594-595dam 500mb ridge will be centered over the Southern Plains at the start of the long-term period. A series of weak perturbations on the southern fringe of the ridge will help keep a slight chance of showers and thunderstorms, particularly across coastal counties, in the forecast through Tuesday. With modest subsidence occurring aloft, kept PoPs between 10-20% for now. Better and more widespread PoPs are progged to occur starting Wednesday as the ridge begins to loosen its grip some, leading to slightly more defined/vigorous mid-level perturbations to retrograde over deep south Texas. Didn't make many changes to PoPs, keeping them generally between 20-40% each day, with best chances occurring during the daytime. Still lots of unknowns related to QPF through next week. Current thinking is that amounts should be fairly light overall, totals generally a tenth to a quarter of an inch expected. Stay tuned for updates. Temperatures will remain fairly seasonal through Tuesday, with highs in the mid-upper 90s and lower 100s. Lows will stay in the mid-upper 70s across inland locations. High temperatures will take a dip a few degrees in the afternoon during the second half of the week as cloud cover and precipitation chances increase. Heat indices will reach 103-110 degrees most days. && .MARINE (Now through Sunday): Large swells from Grace will continue to lead to hazardous marine conditions across the lower Texas Gulf waters today. Buoy 020 is currently reporting SE winds around 12 knots with sea heights of 8.9 feet and a period of 11 seconds. Observation platforms along the Laguna Madre this morning indicate winds of around 10 knots. Light to moderate east to southeast winds will prevail through the period. Latest model guidance suggest that Gulf seas may remain elevated through this evening. Therefore, the Small Craft Advisory have been extended until 1 AM tonight on the Gulf waters. Isolated to scattered showers and thunderstorms across the coastal waters today may produce brief heavy rainfall and gusty winds. Sunday night through Thursday: Gulf seas will continue to improve Sunday night through Monday as swell continues to decrease. Generally favorable marine conditions are expected to prevail on the Gulf and on the Laguna Madre through the long-term period. Winds will remain light to moderate out of the east or southeast with wave heights around 2 to 4 feet on the Gulf. Showers and thunderstorms will be possible each day and night as weak upper- level disturbances combine with deep tropical moisture, especially on Wednesday and Thursday. && .PRELIMINARY POINT TEMPS/POPS... BAYVIEW/PORT ISABEL 92 78 93 79 / 30 10 10 10 BROWNSVILLE 95 79 96 77 / 30 10 10 10 HARLINGEN 95 77 97 76 / 30 10 10 10 MCALLEN 98 76 99 77 / 30 0 10 0 RIO GRANDE CITY 100 75 101 75 / 30 10 10 0 SOUTH PADRE ISLAND 87 83 88 82 / 30 10 10 10 && .BRO WATCHES/WARNINGS/ADVISORIES... TX...High Rip Current Risk through Sunday morning for TXZ256-257-351. High Surf Advisory until 7 PM CDT this evening for TXZ256-257- 351. Coastal Flood Advisory until 1 PM CDT this afternoon for TXZ256- 257-351. GM...Small Craft Advisory until 1 AM CDT Sunday for GMZ150-155-170- 175. && $$ This product is also available on the web at: https://weather.gov/rgv Short Term/Aviation...63-KC Long Term/Upper Air...67-Mejia